Flagstone Patio Clues

If I had a buck for every improperly installed flagstone patio, I would not be writing this - unless of course I were in the Bahamas writing on a lap top - Arizona seems to love this type of patio. I honestly believe the largest percentage of the mistakes I have seen are from recommendations the stone suppliers make when making their sale. I have had countless people tell me: "Well the stone company said, I didn't need a concrete base . . ."

This is a common misunderstanding. Most people with the ambition to undertake this kind of project themselves have probably been exposed to a certain amount of construction advice and background. However the reality is flagstone placed on sand is not the same as brick pavers placed on sand!

Flagstone incorporates mortar joints between the stone - brick pavers do not. They must be approached differently after the initial grading and compacting is done. When two masonry units are adhered together with mortar, the mortar is dependant upon stability to maintain it's adhesion. So when flagstone placed upon sand settles, wriggles or jogs any at all - as little as 128th of an inch, the adhesion is breached and a crack appears. Once you have a crack it will act as a relief for expanding and contracting during temperature changes as well as further and farther wriggling and jogging. As this movement happens time and time again, over time grains of dirt and sand get trapped in the crack and during the next expansion period the pressure will continue to enlarge the crack until it finally begins to actually crumble - unsightly to say the least.

In more severe cases when there is only loose sand below the stone we have replaced patios where after only a few years there were no sound mortar joints left at all. It is much more expensive to pull up the stone, re-grade, install a new proper base and then relay and grout the stone - as much as 1.75 times the original cost, for this kind of work is very labor intensive.

To be sure your patio will still look beautiful long after your mortgage is paid off, a concrete base is MANDATORY. There are no options! Anything shy of proper in flagstone is throwing away your money.